Recent content by Jon_Logan

Just my personal opinion: After modifying and seeing others who have modified the tube rectifier over to silicon, I would now make a little delay circuit for the plate voltage rectification. Now, if I were to design a circuit for this, would delay the plate voltage, but allow the heaters to...

For a subwoofer application, you might want to consider a Class-D (switchmode) amplifier. The bandwidth that a subwoofer needs is low. That is right in the wheelhouse for Class-D amplification. If there are sonic issues to be had with Class-D amplification, low frequencies wouldn't be...

If you need high output levels (large voltage swings) and want Class A output stage bias, you'll need to get creative in what to select. The Thresholds, as well as the Nakamichi (PA-7's) both dissipate quite a bit of heat. Most amps have fixed rails that supply the output stage. The...

I believe the Sunfire runs Class A and cool.

Let's just say, you must consider the magnitude of the input to output errors. Electronics, amps, preamps, DAC's, and the like are pretty easy to get right to a point of vanishingly small distortions. Distortions in frequency response, distortions in signal integrity, distortions in phase...

Dismiss which speakers? I can tell you a large portion of what we measured were not optimized. ...even from some well known and highly regarded manufacturers. And no, I ain't mentioning any names.

Well, it should be okay if that's the case. I just wouldn't try get too far out of the amplifier's comfort zone. Things like; don't play it too loud, check the output transformer temperature every once in awhile when you're using it until it has shown to not run too hot. 2 Ohms isn't a huge...

Just to muddy the waters a bit... I was working with a speaker guy some time ago and he was evaluating all kinds of drivers. Some interesting results came out one of the woofer tests. The tests showed that some speakers (some of the most expensive models) did not have their voice coils...

Put your "6 Ohm" speaker on the 4 Ohm tap. That will be kinder to your output transformer. I would recommend against adding a series resistor. The result of adding the resistor will be a frequency response that is highly affected by the speaker's impedance curve.... ....lot's of...

This should be a 'sticky'.

Nice. Good job! :huge:

These'll probably work: http://www.digikey.com/product-detail/en/GP02-40-E3%2F54/GP02-40-E3%2F54GICT-ND/2880333

In m opinion (and I think Sregor's), you really need to check the waveform at the top of the caps. Your measurement show the the frequency sensitivity shows that the 235uF cap is not shunting enough low frequency signal to ground. .....allowing it to (prematurely) trigger the protection...

I'd be looking into that component named "Selemax". That tells me it might be a selenium rectifier (x2). Selenium's tend to get resistive and develop large voltage drops. Can you wrangle a schematic?

Hmmm. I think I'll wait until I hear the speakers sound bad. I used to work with a speaker guy and we did some measurement with different tweeters. It appeared that harder domes all had an 'Oil can" effect, where the dome would have a mode at some frequency where the dome did not move in...